From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D4482C3F6B0 for ; Thu, 28 Jul 2022 11:46:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237034AbiG1LqT (ORCPT ); Thu, 28 Jul 2022 07:46:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50642 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236956AbiG1LqQ (ORCPT ); Thu, 28 Jul 2022 07:46:16 -0400 Received: from mail-io1-xd29.google.com (mail-io1-xd29.google.com [IPv6:2607:f8b0:4864:20::d29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D3B3051A27 for ; Thu, 28 Jul 2022 04:46:12 -0700 (PDT) Received: by mail-io1-xd29.google.com with SMTP id v185so1161371ioe.11 for ; Thu, 28 Jul 2022 04:46:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20210112.gappssmtp.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=ZTAI4NBWGTQ5h3Og/iXOFE6+j1LyXYJBHvMW6aUVVzs=; b=3yuVzJ0kJ50eg55Qut9vgq+oU18lNCriJe7K+l/NMy1M1TeJu/Cvgm2OSsSllF4CtD 7yLRDb3+hTj7inXwlwwyor84uWesrJQdHqh+s3ypreV2jOUH04k7o9JDQneNozHUjMne nIwpEFe0sMjHsKBY94w/2VZhwckL4ko5Mf7mxCNCMogbU47WIemkLqdSUVq+MhCCDdeB E+4lniUGs1Jq8dnleXXg/cO25yiptnB1cXcDtUTFnUZMnLCAWDPXtbxAqIJocfFDmnMt ljCzrjDtUkho540gcPKjgZhsK3Qx247NMazeZhqYcqVjrMW+LboIngd3b7vTW8EIM1Mf c7Xg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=ZTAI4NBWGTQ5h3Og/iXOFE6+j1LyXYJBHvMW6aUVVzs=; b=3sv6qUyc9imdgUu9WHGG4yZPpcPN+mRN0iHfkAbBj9ymIvurNVsM1K5JlfnhEdl41k p+3Jpg53QzFqOe/PzhqdpVHa3pgoOjCPEaJvHjpmJx/OuRkSaftKz3So1AcYnGbZVOqu hj5MCLoIFv2Xd/4xFqbBrwdULMts5Vdwy0aurqySBJe38JQZjyesSUSBWixieGJBLKuq 5hT7tEwQc5w4Fko6wD6pcLoqnFjce6s/UGBVYvGci/iqGxwsdcM+lkq+NfGw/5wPsXQ8 JUO0BduQg47TrIglR3QHsL/+wHoRMYaLuLr4Trf0W28QTk2FzmvM7AR9FKsHfnETlaiZ JzDw== X-Gm-Message-State: AJIora9ZkbLFmBN+aj8/LTxXQOR1zR9k33oEZrSbdf+n8xUynq/wykZ5 Vi8C2Oq4IeCEJ9YWAlz+MqSHIK7WP6fgDQvoMcFatw== X-Google-Smtp-Source: AGRyM1ugrvrSsb7yRxRfEHxgKZdj4iicx5noLl7XxjN5iOiB+xVZH44oPJIYfkMBjU1FtW9yPjkMrkbXYKHpcaVHK1M= X-Received: by 2002:a05:6638:2486:b0:33f:85cb:f387 with SMTP id x6-20020a056638248600b0033f85cbf387mr10458707jat.247.1659008771414; Thu, 28 Jul 2022 04:46:11 -0700 (PDT) MIME-Version: 1.0 References: <20220728063856.72705-1-zhangjiachen.jaycee@bytedance.com> In-Reply-To: From: Jiachen Zhang Date: Thu, 28 Jul 2022 19:46:00 +0800 Message-ID: Subject: [PATCH] ovl: only WARN_ON_ONCE() if dentry is NULL in ovl_encode_fh() To: Miklos Szeredi Cc: overlayfs , linux-kernel@vger.kernel.org, Hongbo Yin , Tianci Zhang Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-unionfs@vger.kernel.org On Thu, Jul 28, 2022 at 4:57 PM Miklos Szeredi wrote: > > On Thu, 28 Jul 2022 at 08:39, Jiachen Zhang > wrote: > > > > Some code paths cannot guarantee the inode have any dentry alias. So > > WARN_ON() all !dentry may flood the kernel logs. > > > > For example, when an overlayfs inode is watched by inotifywait (1), and > > someone is trying to read the /proc/$(pidof inotifywait)/fdinfo/INOTIFY_FD, > > at that time if the dentry has been reclaimed by kernel (such as > > echo 2 > /proc/sys/vm/drop_caches), there will be a WARN_ON(). The > > printed call stack would be like: > > > > ? show_mark_fhandle+0xf0/0xf0 > > show_mark_fhandle+0x4a/0xf0 > > ? show_mark_fhandle+0xf0/0xf0 > > ? seq_vprintf+0x30/0x50 > > ? seq_printf+0x53/0x70 > > ? show_mark_fhandle+0xf0/0xf0 > > inotify_fdinfo+0x70/0x90 > > show_fdinfo.isra.4+0x53/0x70 > > seq_show+0x130/0x170 > > seq_read+0x153/0x440 > > vfs_read+0x94/0x150 > > ksys_read+0x5f/0xe0 > > do_syscall_64+0x59/0x1e0 > > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > > > So let's replace WARN_ON() with WARN_ON_ONCE() to avoid kernel log > > flooding. > > Better just drop the WARN_ON() completely in that case, since it's a > normally occurring condition. > > Thanks, > Miklos OK. I will send the v2 patch later. Thanks, Jiachen